It is commonly known to put barred metal barriers around windows and doors to deter unauthorized entry therethrough and/or provide protection against projectiles. The metal barriers for doors or windows may be fixed in place or hinged with one or more locks securing one or more marginal edges to a barrier support frame or building structure.
In the case of barred or grilled metal window barriers, they are often simply bolted to a surrounding window frame or structure with the bolt heads modified or welded to the barrier support frame to prevent barrier removal and a potential access point.
Although these barred metal door and window frames provide excellent security from intruders they also provide a similar barrier to those within trying to exit in emergency situations, and others desiring emergency entry from outside in the situations.
In the case of barred or grilled metal window barriers which are not hinged, no emergency entry or egress is possible and those barred or grilled metal door or window barriers which are hinged are generally deadlocked or padlocked which does not allow quick entry or egress in the case of an emergency without ready access to both the door and the door lock key or the like.
Many premises which are susceptible to unauthorized entry through doors or windows, such as schools, police stations and the like, place barred or grilled metal barrier around windows such that once installed they need to be cut away or have a weld or rounded bolt head cut away in order to remove them. As noted above, these barred metal barriers provide excellent security, however, every time a window is broken it must be replaced from the outside requiring the barred metal barriers to be cut away from a window.
In the case of schools for example window breakages are very common and the need to fully remove a barred metal window frame that is fixed there around is significantly more expensive than simply replacing the window. Unfortunately, most windows are designed to be replaced from the outside necessitating the expensive removal and replacement of barred metal window frames when windows are broken.
This is also the case in conventional door-type barriers which include a locking device such as a dead latching lock or other keyed lock in which a latch engages with a strike plate disposed in a predetermined location around the doorframe. In some cases, the strike plate includes a hinged trailing edge which can be electromechanically biased towards an engaged position to retain a door latch in the closed position and to rotate freely against the force of the latch when the electromechanical lock is actuated thereby allowing the door latch to move the trailing edge of the strike plate so as to open the door. It is noted that proximity readers or keys are most often used to engage or disengage the door latch from the strike plate. In the case of standard door deadlocks, a key is normally required.
These locks provide a particularly useful security barrier, however, as with hinged barred window frames it is often difficult to egress through such deadlocked doors in an emergency situation, particularly for the elderly or in cases where people are disorientated. That is, without the key or proximity card and clear conditions to the door, the door can be very difficult to open.
Indeed, all doors and windows which are closed for security reasons include an electromechanical or mechanical lock, or are completely fixed shut. In these cases, it is extremely difficult to enter or egress in emergency situations. For example, recent nightclub fires in Chicago, Ill. killed many people due to many doors and windows being permanently fixed shut or completely locked shut. With some of the doors, nightclub staff having appropriate keys were unable to move to a door and unlock it.
It is also the case that linear motion doors such as train doors are biased and locked in a closed position when power is removed from a train. In these cases, it is only possible to access a train carriage by smashing a window or prying open doors. The latter method can be very difficult, even to emergency services workers, as the doors are designed to remain secure against unauthorised entry.
In other locations where barriers are found, such as high security fencing around the boundary of sporting arenas, many people have died due to crowd surges and people being crushed against the fences. The fences can be removed, however an arena official with an appropriate key to a lock needs to be on hand. Past events have shown that these fences and their quick removal are grossly inadequate.